netdev - Re: [PATCH 1/2] workqueue: Catch more locking problems with flush

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Message-ID: <20120420052633.GA16219@zhy>
Date:	Fri, 20 Apr 2012 13:26:33 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	netdev@...r.kernel.org, Ben Dooks <ben-linux@...ff.org>
Subject: Re: [PATCH 1/2] workqueue: Catch more locking problems with
 flush_work()

On Thu, Apr 19, 2012 at 11:36:32AM -0700, Stephen Boyd wrote:
> Does looking at the second patch help? Basically schedule_work() can run
> the callback right between the time the mutex is acquired and
> flush_work() is called:
> 
> CPU0                        CPU1
> 
> <irq>
>   schedule_work()           mutex_lock(&mutex)
> <irq return>
>     my_work()               flush_work() 
>       mutex_lock(&mutex)    
>       <deadlock>

Get you point. It is a problem. But your patch could introduece false
positive since when flush_work() is called that very work may finish
running already.

So I think we need the lock_map_acquire()/lock_map_release() only when
the work is under processing, no?

Thanks,
Yong
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